"He wasn’t erratic or nervous … just walking down the aisle, randomly firing"

Houser, from Phenix City, Alabama, had been staying in a local Motel 6 in recent weeks. Police said the gunman was "estranged" from his family but there was no indication what drove him to carry out the killings.

Image: John HouserLinkedIn

Investigators found wigs, glasses, and disguises in Houser's room and his vehicle had a switched license plate on it, Craft said, suggesting he originally intended to flee the scene.

About 100 people were watching the 7:10 pm. (8:10 p.m. ET) showing of “Trainwreck” at the Grand Theatre 16 when they heard a popping sound 20 minutes into the movie.

“A lot of the people thought it was part of the film,” witness Josh Doggett, 32, told NBC Los Angeles. There was a pause, but when the firing resumed “everyone started climbing over the seats,” he said.

“In the top left of the theater was a man shooting. He was kind of a middle-aged gentleman in a polo shirt,” he said. “He wasn’t erratic or nervous … just walking down the aisle, randomly firing.”

“It looks like he spotted the officers coming in and he turned around and went against the crowd and he fired a single gunshot,” Craft said.

In a neighboring theater, patrons heard the faint gunshots over the sound of their movie. "I heard three pops, then ... about 10-15 seconds later the sirens went off and the PA system told everyone to evacuate the building," said Jalen Fernell, 20, who was watching “Southpaw” with friends.

Outside, they realized the scale of the horror inside. "There was a middle-aged female lying down, she was shot in her leg and there was blood," Fernell said. "She said she was shot inside the theater and and some guys had picked her up and brought her outside and put her on the curb."

Appearing on Friday's TODAY, he told Matt Lauer: "I’ve never experienced anything like this before. It was the last thing I thought would happened when my friends texted and said, ‘Let’s go to the movies.'”

"Trainwreck" is a romantic comedy starring Amy Schumer, who tweeted:

My heart is broken and all my thoughts and prayers are with everyone in Louisiana.